[net,v2,0/3] net: dsa: mv88e6xxx: fix MV88E6393X PHC frequency on internal clock

Message

Shenghao Yang Oct. 6, 2024, 2:59 p.m. UTC

The MV88E6393X family of switches can additionally run their cycle
counters using a 250MHz internal clock instead of the usual 125MHz
external clock [1].

The driver currently assumes all designs utilize that external clock,
but MikroTik's RB5009 uses the internal source - causing the PHC to be
seen running at 2x real time in userspace, making synchronization
with ptp4l impossible.

This series adds support for reading off the cycle counter frequency
known to the hardware in the TAI_CLOCK_PERIOD register and picking an
appropriate set of scaling coefficients instead of using a fixed set
for each switch family.

Patch 1 groups those cycle counter coefficients into a new structure to
make it easier to pass them around.

Patch 2 modifies PTP initialization to probe TAI_CLOCK_PERIOD and
use an appropriate set of coefficients.

Patch 3 adds support for 4000ps cycle counter periods.

Changes since v1 [2]:

- Patch 1: "net: dsa: mv88e6xxx: group cycle counter coefficients"
  - Kept MV88E6250_CC_SHIFT and MV88E6XXX_CC_SHIFT to retain context.
  - Made newly added coefficient structures static.

- Patch 2: "net: dsa: mv88e6xxx: read cycle counter period from hardware"
  - Removed fallback behavior on failure to read the TAI_CLOCK_PERIOD
    register or an unrecognized cycle counter period.

- Patch 3: "net: dsa: mv88e6xxx: support 4000ps cycle counter periods"
  - Made newly added coefficient structure static.

Thanks,

Shenghao

[1] https://lore.kernel.org/netdev/[e-mail]/
[2] https://lore.kernel.org/netdev/[e-mail]/

Shenghao Yang (3):
  net: dsa: mv88e6xxx: group cycle counter coefficients
  net: dsa: mv88e6xxx: read cycle counter period from hardware
  net: dsa: mv88e6xxx: support 4000ps cycle counter periods

 drivers/net/dsa/mv88e6xxx/chip.h |   6 +-
 drivers/net/dsa/mv88e6xxx/ptp.c  | 108 +++++++++++++++++++++----------
 2 files changed, 77 insertions(+), 37 deletions(-)